Thermoplastic molding compositions based on poly(butylene terephthalate) (PBT) are used in various applications. However, PBT molding compositions generally cannot be made from recycled sources of PBT due to the lack of availability of large post-consumer or post-industrial supplies of PBT scrap materials. Polyethylene terephthalate (PET), unlike PBT, is made in much larger quantities and is more easily recovered from consumer wastes.
With increasing demand for conserving non-renewable resources and more effectively recycling underutilized scrap PET, improved and less costly processes for deriving PBT from scrap PET materials are sought, in particular if the resulting derived PBT compositions possess desirable physical properties such as tensile and impact strength, and thermal properties. To that end, the preparation of polybutylene-co-adipate terephthalate (PBAT) copolyester prepared using post-consumer (recycled) poly(ethylene terephthalate) (PET) has been disclosed. The resulting copolyester contains the impurities ethylene glycol (EG), and isophthalic acid in the backbone, both artifacts from using post-consumer (recycled) PET during the depolymerization process. Such impurities have a negative effect on the melting temperature of the resulting copolymer, making the material less suitable for commercial use. As a result, it is desirable to provide PBAT grades prepared from recycled PET that have reduced concentrations of EG and isophthalic acid.